Off topic - Generator help

Solid_Fuel_Man

So as an experiment today I fired up my cheapo Generac LP3250 propane genny.

Drug out my scope from college and got some wine waves. First is of utility line 120V

Second one is Generac with 2x 1500 watt electric heaters, one on each hot leg of 240V, so nice resistive balanced load. Well it didn't look too pretty. My camera wouldn't capture the whole waveform in the daylight. But I think you get the picture.

ChrisJ

Solid_Fuel_Man said:

So as an experiment today I fired up my cheapo Generac LP3250 propane genny.



Drug out my scope from college and got some wine waves. First is of utility line 120V



Second one is Generac with 2x 1500 watt electric heaters, one on each hot leg of 240V, so nice resistive balanced load. Well it didn't look too pretty. My camera wouldn't capture the whole waveform in the daylight. But I think you get the picture.

I'm confused @Solid_Fuel_Man
Why does this concern you?

Leonard

Did the Generac have electronic reg or cap "reg" ?
I had a older red 5,5 kw one that had electronic reg.

I've seen an electronic voltage reg gen make a jittery curve similar to that. I helped a guy who accidentally had a small cap across gen's 120V output, that caused it to do that. . See pic in post 10 of this link https://www.smokstak.com/forum/showthread.php?t=125255&highlight=capacitance
Without cap load gen made a clean sine wave.

Gens can only take VERY little capacitance (leading load) before they run into trouble, more and can cause heating of windings and may cause loss of voltage control, top of 3-rd page --->https://www.cumminspower.com/www/literature/technicalpapers/PT-6001-ImpactofPowerFactorLoads-en.pdf

Can't help but wonder if the cap "regulator" on these somehow responsible for that jitteryness.

The Onans typically make a sine wave very much like your utility pic ( a real sine wave)

ChrisJ

So,

Regardless of what's causing it and how awesome Onan is, what exactly would have a problem with this and why?

NY_Rob

^ ECM pumps may have real problems with deformed/distorted sine waves.
I test ran my Grundfos Alpha on the similarity bad output from a sub $100 "Back Office UPS" and it (the Alpha) was literally singing... and not in a good way. I'm guessing that running it on that crappy UPS output would have burned out the Alpha in short order.
An old 007 pump probably would have run fine on the same UPS.

Modern electronics with computer controls, etc... do not like distorted wave inputs.

Leonard

I never knew some gens made waveforms this slopply. Now I start to understand why people talk about poor quality sine waves and end up going overboard wanting Honda inverter gens.

I don't know a lot about cap regulated gens, so I don't really know what's causing the sloppyness. Sorry to have say it , but cap reg gens are a cheapie design. I suspect they chose to make waveform compromises to produce a gen for the low end market.

Been talking to gen experts on Smokstak.com, Onan sub-forum, they have some ideas. I think it would be a good idea to discuss this with them. They are pretty good even with cap reg gens.
https://www.smokstak.com/forum/showthread.php?t=181891

ChrisJ

Leonard said:

I never knew some gens made waveforms this slopply. Now I start to understand why people talk about poor quality sine waves and end up going overboard wanting Honda inverter gens.

I don't know a lot about cap regulated gens, so I don't really know what's causing the sloppyness. Sorry to have say it , but cap reg gens are a cheapie design. I suspect they chose to make waveform compromises to produce a gen for the low end market.

Been talking to gen experts on Smokstak.com, Onan sub-forum, they have some ideas. I think it would be a good idea to discuss this with them. They are pretty good even with cap reg gens.
https://www.smokstak.com/forum/showthread.php?t=181891

Check your PMs when you can Leonard.

Leonard

Found more info on how bad the sinewave can be on cheap gens (likely capacitor voltage regulated gens)

Onan Gens with old saturation voltage reg design (Onan CCK, NH, BF, BA, etc) or real voltage regulators like Onan JB/JC and BGE/NHE types etc make a real nice looking sinewave.

See post #4904 to 4010 of this link
https://www.smokstak.com/forum/showthread.php?t=115080&page=491

sunlight33

https://dam-assets.fluke.com/s3fs-public/3497420_6112_ENG_A_W.PDF

Jamie Hall

@Gordy -- agree with your list, but out here trying to run a farm, I'd add three things: the water pump, the stock tank heaters (that's 5 KW right there on a cold night), and -- while you're at it it's real nice to be able to run a stove burner or two...

Leonard

Direct link to scope pics of an old Onan CCK gen (left) and utility (right).
Shown with no-load . Slight peaking , but a very clean sinewave. I think peaking goes away if add a reasonable load.

Other old Onans are similar, new ones are likely as good , just too new to have seen them yet.

https://photos.google.com/share/AF1QipOSMgHYIirSpLpbyWqcXFsc8Bryul8p64kmx7f7yRfkO3wYP-oOy_lQ6AQoJKZc0w?key=c1pNeEN1VzhUTlF1YmlGS21NMUJ3c3dyUTVyT3B3

ChrisJ

Leonard said:

Direct link to scope pics of an old Onan CCK gen (left) and utility (right).
Shown with no-load . Slight peaking , but a very clean sinewave. I think peaking goes away if add a reasonable load.

Other old Onans are similar, new ones are likely as good , just too new to have seen them yet.

https://photos.google.com/share/AF1QipOSMgHYIirSpLpbyWqcXFsc8Bryul8p64kmx7f7yRfkO3wYP-oOy_lQ6AQoJKZc0w?key=c1pNeEN1VzhUTlF1YmlGS21NMUJ3c3dyUTVyT3B3

@Leonard

Do you have an Onan tattoo?

ChrisJ

BTW,

Here's a quick rendering of what the generator I'm building will look like when done. Kind of.

10KW LPG / NG.
Yes, it's output is noisy with poor regulation but it's good enough for emergency power.

turtmaster

ChrisJ, I was the one who had posted the screenshots of the generators in the links, on smokstak.com,

Also here is some links to screenshots of, on the left a capacitor excited Coleman powermate 2500w, and a portercable 10kw with a Honda gx620 and a mecc-alte capacitor excited brushless generator head on the right, I think it might be the exact same model number, gen head as the one that you have.
Notice how much cleaner the quality, mecc-alte head's power is.

https://photos.app.goo.gl/tRQYmJKi6Kp9ujBV8

Leonard

I had posted the links to clean Onan waveforms since some people here had talked about going to Honda inverter gens to get a clean waveform.

To me Inverter gens seem overkill, very expensive, and needless option as they cost about $1500+. Whereas these old Onans running are $300-500 and are about bulletproof (last about forever with proper maintenance--- change the oil) . Plus with an inverter gen if that modual fails it's about $1000+ for new one in a box (install is extra $$). So I don;t think modern inverter gens are very cost effective either. I have 2 Onans: 7NHM and 7.5JB

no tatoo ... but I do see the high valve in Onans. They were built to last. In today's dollars a new CCK might have gone for equivalent of ~ $4-5k, so you can see the quality. Seen an Onan 6.5NHD with 8700 hours on it for sale on Craigslist, ad said needs engine rebuild. Probably not going to see that type of hours from a Honda.

ChrisJ

> @turtmaster said:
> ChrisJ, I was the one who had posted the screenshots of the generators in the links, on smokstak.com,
>
> Also here is some links to screenshots of, on the left a capacitor excited Coleman powermate 2500w, and a portercable 10kw with a Honda gx620 and a mecc-alte capacitor excited brushless generator head on the right, I think it might be the exact same model number, gen head as the one that you have.
> Notice how much cleaner the quality, mecc-alte head's power is.
>
> https://photos.app.goo.gl/tRQYmJKi6Kp9ujBV8

Turtmaster, thank you for sharing.

I thought the brushless alternators were really bad. Why is that one fairly decent?

turtmaster

I can't quite remember, but one of the factors, might be the mecc-alte, might have more "skew" (angle) in the winding slots.
Long ago I had found an article, that gave a list of factors, but I can't currently find it, but one factor is the "construction" of the generator head itself, another thing that you have to remember is, that powermate, was probably ~$300 new, total cost, and that mecc-alte generator head alone is probably like ~$800-$1000+

sunlight33

You can also reduce THD through a power conditioner, here's one: https://www.alliedelec.com/product/solahd/63-23-112-4/70098593/

(edit: it's only rated 120VA, they make models with larger ratings)

Leonard

Think those were discussed in Onan forum of Smokstak.com . Think consensus was gens don't play well with them, think stabilizers are a capacitor/transformer resonant system.

Not sure if they present a capcitive load to gen but--- In general gens can't take much capacitive (leading power factor --PF) load at all before losing voltage control, add more and start to get genhead damage. There are also limits on inductive loading gens can take too, but gens are much more tolerant of lagging PF (inductive loads) than leading PF (cap loads).

Technical artical on tolerable load PF for gens. See top of 3-rd page.
of attached file.

Stabilizers ....Might be a good idea to first characterise PF over load and maybe voltage of those loads on utlity power before connecting to a gen. And then test again including scope waveform and ( $20 kill-a-watt meter measures PF and lot more) .

Here at house I put a cap across utility power and amps ( ~ 2) measured right on the money, so utility power has negligible inductance. Suspect gen stator has a LOT of inductance (source impedance is not low).

Because of this , a cap load on gen can cause a sloppy waveform even on a super clean waveform gen . See post #10 https://www.smokstak.com/forum/showthread.php?t=125255&highlight=capacitance
. This likely applies to ANY gen.

nibs

A thought about using a NG genset to run the boiler, you could use the waste heat from the engine to assist the boiler in hydronic systems. I took the radiator off the genset in my coach and plumbed it into the main engine coolant system, on a chilly morning, starting the generator gives me a warm engine for starting and a warm living room. If you used a water bath exhaust system (as in sailboats) you would have a very quiet & efficient generator.

Leonard

It's nice co-generation at home too if you use it enough to pay for the equipment. Water cooled gasoline powered gen at full load think you'll see ~ 35% of fuel's energy come out as hot cooling water, 47% out the exhaust pipe, and 18% out as electrical power. If use water cooled exhaust manifold (closed loop boat type) can salvage BTUs from exhaust too.

1 gal gasoline = about 125kBTU, my Onan 7kw 7NHM gen uses .4 GPH no-load 1.3 full load. Diesels use ~ 1/2 these numbers.

Water bath would likely become acidic from exhaust gases.

There are ways to really make gens quite. Water cooled are quieter. Some gens have very good mufflers. With my Onan 7NHM the exhaust is so quite that mechanical engine noise is louder, but it's air cooled (nosier).

Another idea old Onan literature promotes is pipe exhaust into a 55 gal barrel buried underground.... makes for a cheap large exhaust pulse expansion chamber (muffler).

Also can add box around gen lined with fiberglass insulation to absorb sound coming off engine.

Solid_Fuel_Man

I cant imagine using NG as a "backup fuel". Seems like you would just be relying on the grid. Just the NG grid instead of electric grid. I want a fuel which is kept onsite which I have complete control over.

ChrisJ

Solid_Fuel_Man said:

I cant imagine using NG as a "backup fuel". Seems like you would just be relying on the grid. Just the NG grid instead of electric grid. I want a fuel which is kept onsite which I have complete control over.

You can't imagine using a fuel that practically never goes out as backup.

Interesting.

By the way, when electric goes out so do gasoline and diesel pumps.

Jamie Hall

Solid_Fuel_Man said:

I cant imagine using NG as a "backup fuel". Seems like you would just be relying on the grid. Just the NG grid instead of electric grid. I want a fuel which is kept onsite which I have complete control over.

Ditto. At least in these parts (New England and downstate New York), natural gas is less reliable than the electric grid when you really need it -- like today.

ChrisJ

Here in NG natural gas practically never goes out.

During Sandy only areas near the coast lost it to my knowledge but we all lost gasoline and diesel except areas that had electric.

The comment is a bit strange overall because if you lose electric, no matter where you are you lose gas pumps. So that makes pretty much all gas portable generators useless unless you have a huge stockpile on hand and we all know how well modern gas ages.

That leaves LPG. I suppose if NG is that unreliable where you are (and yet you feel it's reliable enough for heat) then I guess you need to choose either diesel or LPG.

For me and many others, NG is by far the best choice.

stlvortac

Here’s my fav video comparing brushed vs brushless gens on an oscilloscope. Obviously it’s comparing apples to oranges as portability is concerned but I’d love to get a surplus generator for home backup. Most of them are extremely underrated, he’s powering centeral air on a ‘5kw’ generator in the video.

https://youtu.be/QNo1mUCpQnI

ChrisJ

I should put a scope on my SCR condenser fan controller to show it's chopped distorted output.

I haven't, because I don't care and I know it's ugly and bad for the motor. But, the pros outweigh the cons.

pecmsg

ChrisJ said:

Here in NG natural gas practically never goes out.

During Sandy only areas near the coast lost it to my knowledge but we all lost gasoline and diesel except areas that had electric.

The comment is a bit strange overall because if you lose electric, no matter where you are you lose gas pumps. So that makes pretty much all gas portable generators useless unless you have a huge stockpile on hand and we all know how well modern gas ages.

That leaves LPG. I suppose if NG is that unreliable where you are (and yet you feel it's reliable enough for heat) then I guess you need to choose either diesel or LPG.

For me and many others, NG is by far the best choice.

No electric No LP either. there pumps are electric!

Jamie Hall

It's a very real problem, @ChrisJ -- and like most real problems, there's no one size fits al (and sometimes no good solution, period!)l. In most areas of the country I would agree that NG is probably the most reliable. In some, not so much -- and of course where I am not an option; not available at all, and not likely to be anytime in the near future (most of the more "rural" areas of New England are that way).

The three places I care for are illustrative. One -- forced air heat -- has no provision for backup at all. Another one -- hot water -- also has no backup for heat, although the water is gravity spring fed (and yes it's checked for quality!). Solution to that one if the power goes out is a quick trip in the 4WD and drain the puppy. And swear. The third, where Cedric lives, has gasoline generators which can handle most of the load and, since it is a farm, has enough gasoline on hand at any one time to go at least a week. More than a week? Things get interesting. First priority is the animals. Second is water for people. Both would come from the main farm pond -- and we have treatment on hand for that (it's not the cleanest water in the world). Drain the plumbing and keep an eye on basement temperatures (don't drain Cedric unless you have to!).

ChrisJ

My 10kw generator can run NG or LPG and I also have a 4kw gasoline generator so I guess I'm covered.

pecmsg

I've got 2 boats combined 175 Gals Gas not an issue ether!

ChrisJ

> @pecmsg said:
> I've got 2 boats combined 175 Gals Gas not an issue ether!

How do you keep the fuel fresh in those?

pecmsg

In the winter stabilizer.

Summer a lot of Fishing!

sunlight33

Also an issue with those on city water, but I presume the town got some kind of generator backup for the water supply. There will be panic if water goes out for more than 2 weeks.

Leonard

Here even city sewer pumps have gen backup.

Nat gas used to be very reliable , now maybe not. During some emergencies like flooding they even shut it off nowdays.

Liekly 250 gal propane tank is highest reliability option for long term fuel storage but tank is $$$$$ ( would last ~ 250 hr run time (~ 10 days @ 5kw load , 7kw gen). They have propane conversion kits for gasoline gens, not hard, ~ $100

I have gasoline gen. Key to keeping gas good long term is SEAL the containers. Ethanol will pull water out of air, that is main problem with modern gasoline. I've seen a watery layer on bottom of a pizza pan with gas in it after 15 minutes on cold humid day.

SEAL gas jug air tight and it can't get wet. Also if don't draw last inch out of tank you likely won't suck the water layer. Otherlong term issue is lighter molecular weight components of gasoline can evaporate IF container is not SEALED air tight.

Gas stabilizer DOES help, had 1 year old gas in regular vented gen tank, it run fine.

Currently between 2 cars ( 20 gal each) and tightly sealed gas jugs I've got ~ 65 gals of gasoline. I have three 6 gal gas jugs, they are heavy and I want more storage . Found that 1 gallon motor oil and antifreeze jugs are made of same plastic as gas jugs ( #2 recycling mark). So I have ~ 10 of them sealed and stored outside under a rubbermaid tote box to keep snow/rain off them. Plan on tapping car fuel line to car engine and adding valve/hose to let car pump the gas into gen tank for refill.

For ready to run convince I plan on converting a 100# propane tank to a ~ 23 gal gasoline tank and connecting it to my gen. SEALED with ~ 25 psi relief valve, stored in shade of my trees. That should solve ethanol moisture and evaporation issues. Will give 1-2 day total run time, 7 kw gen, (load dependent)

Fuel storage solution depends on where you are. I have no nat gas, I'm on edge of a large city 100k+. But city is feed by likely 1/2 dozen electrical substations, so not concerned that all of it's MANY gas station will be down. Would take cross country powerlines going down to black out whole city and shut down all gas stations. Different people have different best solutions.

Diesel gen would be good if heat with oil (240 gal tank). It could run a diesel, watch gelling temperature.

ChrisJ

> @Leonard said:
> Here even city sewer pumps have gen backup.
>
> Nat gas used to be very reliable , now maybe not. During some emergencies like flooding they even shut it off nowdays.
>
> Liekly 250 gal propane tank is highest reliability option for long term fuel storage but tank is $$$$$ ( would last ~ 250 hr run time (~ 10 days @ 5kw load , 7kw gen). They have propane conversion kits for gasoline gens, not hard, ~ $100
>
> I have gasoline gen. Key to keeping gas good long term is SEAL the containers. Ethanol will pull water out of air, that is main problem with modern gasoline. I've seen a watery layer on bottom of a pizza pan with gas in it after 15 minutes on cold humid day.
>
> SEAL gas jug air tight and it can't get wet. Also if don't draw last inch out of tank you likely won't suck the water layer. Other issue is long term lighter molecular weight components of gasoline can evaporate IF container is not SEALED air tight.
>
> Gas stabilizer DOES help, had 1 year old gas in regular vented gen tank, it run fine.
>
> Currently between 2 cars ( 20 gal each) and tightly sealed gas jugs I've got ~ 65 gals of gasoline. I have three 6 gal gas jugs, they are heavy and I want more storage . Found that 1 gallon motor oil and antifreeze jugs are made of same #2 (recycling mark) plastic as gas jugs. So I have ~ 10 of them sealed and stored outside under a rubbermaid tote box to keep the snow/rain off them. Plan on tapping car fuel line to car engine and adding hose to let car pump the gas into gen tank for refill.
>
> For ready to run convince I plan on converting a 100# propane tank to a ~ 23 gal gasoline tank and connecting it to my gen. SEALED with ~ 25 psi relief valve, stored in shade of my trees. That should solve ethanol moisture and evaporation issues.
>
> Fuel storage solution depends on where you are. I have no nat gas, I'm on edge of a large city 100k+. But city is feed by likely 1/2 dozen electrical substations, so not concerned that all of it's MANY gas station will be down. Would take cross country powerlines going down to black out whole city and shut down all gas stations. Different people have different best solutions.
>
> Diesel gen would be good for me, I heat with oil. 240 gal tank in cellar , it could run a diesel.

You don't have natural gas but know it's unreliable now?

I've had natural gas for 38 years and have never seen it get shut off.


Were you in NJ for Sandy?!?

nibs

@Leonard, it would be interesting to run the numbers on lets say a 10 or 12KW generator as both heat source and elec source to take the place of the electrical grid.
I no longer remember the math I used in 1980/83, but even wasting the heat it did not look too bad, now with the interest in hydronics hmmm.

Leonard

Without thinking too hard I can remember on news at least 6 times nat gas was shut off, twice on local flooding, Andover Mass, Newport RI, Sandy@ NJ, Calif earthquakes ...

Co-generation.... I ran the numbers for a guy. Gasoline water cooled Onan gen at full load: ~ 38% of fuel's energy comes out as hot cooling water, 18% as electrical power, rest out exhaust pipe. If use a boat exhaust manifold (close water loop) can recover some of exhaust energy too.

I ran above numbers for ~ 30kw gen , but I believe % will not change much as go up or down on gen size, likely ~ same for different gen manufacturers. 18% out as electrical power is my calculated number for 7 to 40 kw Onan gens, haven't looked at others. 1 gal gasoline = 125kBTU

Problem is unless your off grid then gen likely doesn't run enough to justify equipment costs. And if grid is available, engine wear out is not an insignificant cost.

Guy in Mass has reduced nat gas cost in winter heating season, air cooled gen , HE calculated he could make power ( no heating) for ~ 2 cents less/KWH than utility. But that is EXCLUDING wearout cost of gen, think he pays ~ 18+ cents/KWH. A good gasoline Onan 7.5 JB might have ~10k hours of life before engine rebuild, you'll get there in < 2 years of continuous use. Other BIG issue is gens burn lot of fuel even at no load ( my gasoline 7NHM 0.4GPH at no-load, 1.3 full load)

Solid_Fuel_Man

Before I bought my 500gal LP tank I had considered getting a small single cylinder diesel generator. Run it off fuel oil. Guaranteed to have at least 100 gallons on hand, would likely last many weeks with careful usage. Burn wood for heat and oil was just for backup.

Sold entire oil setup and now have mod/con as backup also gas clothes dryer, and range.

20 pounders for grill and generator, have ACME adapters so I can connect to 500gal tank if I deplete the two 20pounders. But I'm trying not to be a prepper, as my wife already thinks I'm crazy....maybe she is right!

Gordy

Years ago we use to have some one popper diesel generator/ welders at work, Miller’s. They would run 16 hours on a tank of fuel which was about 2 gallons.